Hybrid vehicles have an electric drive (EV) mode, in which the hybrid vehicle travels only by power from the motor-generator, and a hybrid drive (HEV) mode, in which the hybrid vehicle can travel by power from both the engine and the motor-generator. For example, Japanese Patent Provisional Publication No. 2005-221073 discloses a hybrid system that employs a first engagement element that performs connecting/disconnecting actions of a power transmission path between an engine and a motor-generator, and a second engagement element that performs connecting/disconnecting actions of a power transmission path between the motor-generator and drive wheels. Switching between the EV and HEV drive modes occurs depending on a vehicle driving condition (engine/vehicle operating conditions) to improve fuel economy.
According to the technique disclosed therein, the second engagement element is subjected to slip control during the engine starting operation initiated when switching from the EV drive mode to the HEV drive mode, so as to reduce a shock.